The hallmark of wireless telecommunications services is mobility gained by the elimination of wired connections. Indeed, the ability to use a mobile terminal (such as a cellular telephone) to originate and receive calls across a wide range of geographic locations is enabled by the use of an allocated portion of radio spectrum dedicated to transmitting voice, data, and control information. More particularly, mobile terminals send and receive voice, data, and control information from base stations over an air interface. The base station serves as a gateway point between the mobile terminal and a mobile switching center. The mobile switching center provides call processing services and resource allocation for establishing call connections in the wired network which is required for connecting mobile terminals to other parties.
To establish a call, a base station allocates air traffic channels to a mobile terminal for transmitting voice, data, and control information. In one implementation, a traffic channel operates at a carrier frequency comprising time slots during which the mobile terminal transmits data frames (including synchronization bits) to the base station and vice versa. One problem with mobile telecommunications is that synchronization needed to maintain a connection between a mobile terminal and base station is often lost. The most common cause for loss of synchronization is the inability of the terminal or base station to detect the carrier frequency of the traffic channels used in the call. Another cause of loss of synchronization is the inability to receive data frames from the mobile to the base station (or vice versa) in their anticipated time slots due to obstructions such as trees, buildings, tunnels or noise interference. In current implementations, both the serving base station and the mobile terminal wait for each others carrier frequencies (or data stream) to be reinstated for a specified period (a resynchronization "time-out" period) before the loss of synchronization precipitates call release procedures tearing down the existing call in the base station. From the base station perspective, releasing a call results in releasing the air traffic channels and other resources associated with the call. If the base station fails to resynchronize, it sends a call release message indicating disconnect to the mobile switching center so that call connections to the other party (or parties) are released. In the current art, from the mobile terminal perspective, releasing a call involves termination of data traffic on the air traffic channel allocated to the call, and resetting an internal state of the terminal so that new calls can proceed.
Abnormally released calls due to loss of synchronization result in subscriber frustration and a need for reestablishing the call. Reestablishing a call requires re-dialing and reestablishing connections interconnecting the mobile terminal to its parties. Hence, reconnecting disconnected calls not only requires subscriber action but also requires duplicated network action. Therefore, there is a need in the art for efficiently reconnecting mobile calls to decrease subscriber inconvenience and enhance network efficiency when disconnected calls are reconnected.